Dispensing units having multiple chambers for holding different flowable substances are generally known. In one prior art dispenser, the flowable substances are stored in separate compressible chambers within a container, each chamber being provided with a dip tube. Secured to the top of the container is a metering and mixing output section. A metering mechanism includes a shaft on which are mounted a series of cams and a selector dial coupled to the shaft which functions as a control element to rotate the cams, each cam being arranged in the course of rotation to more or less pinch a respective dip tube and thereby determine the volume of constituent flow from each of the chambers into the output section.
Another prior art dispenser for holding metering, mixing and dispensing a mixture of two substances comprises a container having two compartments for containing the two substances and a cylindrical neck at the top of the container containing a first bore and a second bore each communicating with a respective chamber of the container. A cylindrical mixing chamber communicating with the first and second bores is disposed over the cylindrical neck and includes a third bore on a top end thereof for the egress of the two substances. The dispenser also includes a selector dial having a central opening concentrically disposed over the first bore for dispensing the substance from one of the compartments. A plurality of various diameter metering openings are disposed peripherally around the selector dial concentrically disposed to pass over the second bore as the selector dial is rotated such that the substance being dispensed from the other compartment is adjustable.
A third prior art dispenser comprises a cylindrical housing having a dispensing end and a storage chamber enclosing a pair of containers for receiving flowable substances which are removably mounted on a mounting block. The block is provided with a pair of openings on an annular surface having a central projection about which a selector dial rotates. The projection includes a pair of passageways in fixed alignment with the openings so as to conduct a flowable substance therethrough. A regulating disc including a plurality of different sized openings is movably disposed on the annular surface for revolving about the projection. When the disc is moved in response to rotation of the selector dial, a selected disc opening is placed in registry between a block opening and a respective passageway to permit the flowable substance within each container to pass into blending relationship at the dispensing end.
The above-mentioned prior art dispensers provide metering by means of varying the openings of the chambers disposed within the container by means of a dial valve or regulating disc to restrict the flow of material, and thereby alter the proportions of liquid by means of the restriction. These dispensers have erred in their conception that the substances are dispensed by exerting equal pressure on the compressible chambers within the compressible outer container. The results of applying pressure as described when holes are close in diameter does not result in altering the volume of material extruded through the holes in any predictably variable way other than as a function of the amount of pressure exerted. Another disadvantage of the prior art dispensers is that they all employ a relative complex structure involving relative high manufacturing costs.
The present invention overcomes many of the disadvantages inherent in the above-described prior art dispensers by providing an apparatus for dispensing two flowable substances in a user selectable ratio in which the volume flow varies proportionally with the application of pressure in a predictable manner. The dispensing apparatus in one embodiment comprises a container having a dispensing end, a flexible outer wall and a flexible inner diaphragm separating the container into two generally equal chambers having open ends for receiving a different flowable substance. A selector member having a single opening extending therethrough is disposed between the open ends of the chambers and the dispensing end of the container. The selector member is selectively rotatable with respect to the container through a series of positions in which the selector member either completely or partially restricts the open ends of the chambers in proportional ratios. Upon compression of the outer wall of the container, the flexible diaphragm regulates the specific pressure at the open ends of the chambers by distributing the pressure within the chambers in response to the back pressure or lack thereof resulting from the restriction of the open ends of the chambers by the selector member. A pressure differential between the chambers is thus created allowing a predictable flow of substance through each chamber opening. Hence, the present invention overcomes the unpractical designs of the prior art selectable mixing dispensers which only properly function if uniform and constant pressure is exerted on the container, since any variation in pressure alters the resulting output of each flowable substance so as to make a uniform mixed output of the flowable substances at a selectable ratio difficult to achieve.
Another practical advantage of the dispensing apparatus of the present invention is that the structure allows for compact design, thus resulting in more economical construction than prior art dispensers employing metering and mixing devices.